Electromagnetic hydraulic valves of this type are used, inter alia, in valve drives of internal combustion engines in which changes to opening times and closing times of gas exchange valves can be brought about by phase adjustment of a camshaft with respect to a crankshaft using an adjustment device. In this context, the electromagnetic hydraulic valve usually regulates the supply of pressurized fluid to a hydraulic adjustment device of the respective camshaft.
DE 10 2005 053 961 A1 discloses an electromagnetic hydraulic valve which is comprised of an electromagnet and an adjoining valve part. The electromagnet has here a hollow-cylinder-shape coil carrier which is comprised of a plurality of individual parts and accommodates a coil in a completely enclosed fashion between these parts. A radial coil carrier part located within the coil also forms a magnetizable section at an axial end and has in an inner drilled hole a magnet armature which can move axially counter to a restoring spring.
If the coil is then supplied with current via a connection section provided on the coil carrier of the electromagnet, the end section of the inner coil carrier part is magnetized by the generated magnetic field and forms an end pole of the electromagnet. Depending on the current supplied to the coil and the associated magnetization of the end section, the magnet armature is correspondingly moved axially in the direction of the end section counter to the restoring spring. In this context, the magnet armature moves a displaceable control piston which is accommodated in the valve part adjoining the electromagnet. Depending on the position of the control piston set as a result of this, a flow of fluid across the valve part is regulated.
In the case of DE 10 2005 053 961 A1, the end pole for moving the magnet armature is therefore formed by a coil carrier part which is inserted axially into the cylindrical interior space of the coil and whose end region can be magnetized.
Furthermore, DE 10 2006 042 215 A1 discloses an electromagnetic hydraulic valve which is comprised of an electromagnet and a valve part and in which a coil carrier of the electromagnet accommodates a coil in a completely enclosed fashion in an injection-molded encapsulation. In addition, a magnetizable insertion part is placed in the radial inner region of the coil, which insertion part is also supported by the injection-molded encapsulation of the coil carrier and forms an end pole of the electromagnet when the coil is energized. However, in order to prevent moisture penetrating via the injection-molded region of the insertion part, an O-ring is introduced between the coil carrier and the injection-molded encapsulation in the axial direction so that it is positioned in front of the insertion part.
The coil carrier also has, in an interior space, an axially movable magnet armature which carries out a translatory movement under the influence of the magnetized insertion part when the coil is energized, and in the process this coil carrier moves a control piston of the valve part. The valve part is embodied here as a 4/3-way valve so that depending on the position of the control piston pressure medium passes from the pump connection to one of the two working connections, while the respective other working connection is connected to an end-side tank connection.